Fresh water is recognized as a valuable resource. For much of the industrialized world fresh water is treated in a centralized water purification plant to make it potable (that is purified enough to be safely consumed by humans without threat of catching water borne diseases) and then placed in a fresh water distribution system. However growing populations are putting more and more pressure on water sources. Water is required for agriculture as well as for human consumption and there are concerns that water supplies are running low in many areas. Therefore there is a general understanding that there is a need for water conservation.
In many parts of the world droughts can affect the amount of available water. In the case of a serious drought or even if there is a dry spell in certain areas, restrictions can be imposed on the local population's water use. For example there may be a restriction on lawn watering or the like. In severe cases there may not be enough potable water for even basic human needs such as showers and baths. What is desired therefore is way to reduce water consumption and waterwaste.
Water is used by households. Greywater, also referred to as “gray water”, “graywater” or “grey water”, is defined as water which has been used, for example, for washing purposes. Sources for greywater in a home, for example, would be showers, baths and perhaps washing machines and lavatory sinks. Black water, on the other hand, contains sewage and typically is produced by toilets and is directed to a sanitary sewer. Typically in a modern dwelling, all of the water which goes down a drain, from any source, is directed to the sewer, where it is taken to a sewage treatment plant for treatment, prior to being released into the environment. All of the water that is treated in the wastewater treatment plant was first treated in the water purification plant where the water was taken out of the environment and then purified and made potable.
Currently residential homes have two large sources of water consumption, namely, human washing in showers and baths and human waste disposal by toilet flushing. While the specific consumption varies from house to house, in general the water use statistics show that on average about 25% to 40% of water use is in showers and baths and that about 20% and 30% of water use is in toilet flushing.
In the prior art there are systems proposed for using recycled greywater to flush toilets instead of potable water. This has the promise of reducing the demand for water by about 30% or more as well as reducing the load on the wastewater treatment plants. Therefore it is highly desirable. Using recycled greywater for toilet flushing makes sense because the toilet water is primarily for transporting harmful wastes out of the home and so toilet flush water does not need to be potable, even though it currently is in most cases.
However what is required is a system that can capture the greywater and make it suitable for toilet flushing. Thus, the greywater cannot contain so much organic material that it builds up a scum, a bacteria mat or the like within the toilets where it is used. What is required is a greywater recycling system that can reliably capture, condition and recirculate greywater for toilet flushing purposes. Such a system cannot permit the development of foul odors, must be reliable and have certain fail safe measures built into it to ensure that the operation of the system is reliable, clean and uninterrupted. Such a system must be carefully designed to deal with upsets and interruptions to avoid having the operation of the system, and thus the toilet flushing which relies on such a system, compromised.
Greywater recovery systems have been proposed in the past. However such systems have suffered from certain problems, for example, in some prior art systems attempts are made to recapture all water, including washing machine and black water. However, this introduces many more contaminants into the water recovery system and makes it much more difficult to condition the greywater. In other cases the system attempts to only capture shower and bath water. An example of such a system is shown in US Patent Application No. US20080314457. However, in practice, this prior art system has a number of limitations, including, that a unit is required for each bathroom, there is no sterilization, it requires two tanks on each unit and a siphon system inbetween, and thus can only manage a small volume.
Examples of other prior systems include:    U.S. Pat. No. 524,827 issued Aug. 21, 1894    U.S. Pat. No. 621,803 issued Mar. 28, 1899    U.S. Pat. No. 626,244 issued Jun. 6, 1899    U.S. Pat. No. 628,987 issued Jul. 18, 1899    U.S. Pat. No. 800,113 issued Sep. 19, 1905    U.S. Pat. No. 2,992,986 issued Jul. 18, 1961    U.S. Pat. No. 3,126,333 issued Mar. 24, 1964    U.S. Pat. No. 3,335,868 issued Aug. 15, 1967    U.S. Pat. No. 3,680,701 issued Aug. 1, 1972    U.S. Pat. No. 3,956,128 issued May 11, 1976    U.S. Pat. No. 4,009,098 issued Feb. 22, 1977    U.S. Pat. No. 4,025,426 issued May 24, 1977    U.S. Pat. No. 4,334,990 issued Jun. 15, 1982    U.S. Pat. No. 5,006,240 issued Apr. 9, 1991    U.S. Pat. No. 5,009,776 issued Apr. 23, 1991    U.S. Pat. No. 5,472,610 issued Dec. 5, 1995    U.S. Pat. No. 5,980,748 issued Nov. 9, 1999    U.S. Pat. No. 6,123,840 issued Sep. 26, 2000    U.S. Pat. No. 6,423,216 issued Jul. 23, 2002    U.S. Pat. No. 7,300,570 issued Nov. 27, 2007    U.S. Pat. No. 7,785,469 issued Aug. 31, 2010